Graphitization reaction via zinc reduction: How low can you go?

- Isotopic fractionation in the graphitization reaction for 14C AMS was evaluated.
- IRMS δ13C values of graphitized reference materials are reported for 0-50 mg Zn.
- In the studied conditions the absence of Zn limits reaction yield to 50%.
- The use of 10 mg of Zn yields similar fractionation to that using 20 mg.
- The Zn-free reaction produces the same scattering as for the 30-50 mg Zn range.

In a previous work, isotopic fractionation in the graphitization reaction for Radiocarbon Accelerator Mass Spectrometry (14C-AMS) was evaluated for amounts of Zn ranging from 20 to 50 mg. The results have shown that a slightly lower variation in δ3C during graphitization was achieved with less Zn. In the present paper, assuming that low amounts of Zn would provide the best results, we go further and test isotopic fractionation for 0, 10 and 20 mg of Zn in the graphitization reaction. The results show that the use of 10 mg of Zn yields similar fractionation to that using 20 mg, while using only TiH2 and no Zn produces the same scattering for amounts from 30 to 50 mg. The absence of Zn, on the other hand, plays a major role on the reaction yield for the tested conditions, limiting it to 50%.

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